A five-millimeter incision was first applied to an intestine taken from a pig. (2) Two milligrams of nanocomposite were then applied to the cut and (3) irradiated with a laser, resulting in (4) a fluid-tight sealing. (5) The intestine was then filled with fluid to see when it might leak and burst. (Nanocomposite) A dish filled with the nanocomposite; (inset) the gold nanorods within the composite. Image: K. Rege et al., ACS.
Lasers could help weld intestines together with the aid of a novel glue filled with microscopic gold rods, researchers say.
Diseases that affect the bowels include colorectal cancer and inflammatory bowel disease, both of which afflict about 1.5 million people in the United States annually. During surgery to remove diseased tissue, leaks from intestinal holes are common and can lead to life-threatening bacterial infections.
Lasers are already able to weld ruptures in tissues such as cartilage, blood vessels, corneas, livers, urinary tracts, nerves and skin together by causing proteins to fuse. This stitch-free way of sealing holes is especially helpful in places where sutures and staples may not work, such as thin, fragile tissues.
One concern with conventional laser tissue welding, however, is that any welds might be weak. To solve this problem, chemical engineer Kaushal Rege at Arizona State University in Tempe and his colleagues are developing a protein-based glue that can act as a solder that lasers can heat to patch up holes. [See also: Gel Stops Bleeding, Starts Healing Instantly]
When heated, the goo solidifies into an elastic material that can behave "much like a rubber band," Rege said. "Tissues like colons have to transport matter through them, and the elasticity of materials patching up holes is important."
The composite is mostly composed of artificial proteins, but embedded within it are tiny gold rods only 15 nanometers — or billionths of a meter — wide and 50 nanometers long. (In comparison, the average human hair is about 100,000 nanometers wide.) The nano-rods absorb near-infrared light, which passes harmlessly through human tissue for the most part, causing them to heat up enough to coagulate the surrounding proteins in the goo.
The researchers successfully used laser welding and their goo to patch holes up to several millimeters large in pig guts. These welds significantly increased the amount of pressure needed to cause leakage or bursting of repaired tissues and created liquid-tight seals that prevented gut bacteria from sneaking out.
The laser glue should be biodegradable, Rege noted, although tests of it in animals are needed to be sure. The gold nano-rods are also thought to be fairly inert, "although studies are needed to look for any long-term toxicity," he added.
The researchers aim to proceed to experiments with live animals. They also hope their composite might not only be capable of repairing holes, but intestines that have completely been cut in two, Rege said.
Rege, along with graduate student Huang-Chiao Huang and their colleagues, detailed their findings online March 26 the journal ACS Nano.
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